German Patent Application No. DE 35 03 798 A1 describes a method and a device in which the quantity of recirculated exhaust gas is identified from values for the pressure in the intake port of the internal combustion engine with the exhaust gas recirculation system switched on and with it switched off.
German Patent No. DE 28 49 554 C2 describes a device for specifying the composition of the gas content and the volumetric efficiency of cylinders in internal combustion engines. In this device, a mixture of fresh air and recirculated exhaust gas is adjusted, inter alia, as a function of the entire charge of the cylinder. The entire charge of the cylinder is identified by the round-about means of measuring pressure and temperature in the intake manifold.